76 Rockwell Automation Publication ICSTT-RM447M-EN-P - July 2019
Chapter 4 AADvance System Architectures
capacity you have to add I/O base units then the required number of I/O
modules and termination assemblies.
Data Input and Output
A controller can support up to 48 I/O modules in total (on 16 I/O base units);
as an example, here is a controller with four 8 channel T9401 digital input
modules and two 8 channel T9451 Digital Output Modules, giving 32 inputs
and 16 outputs.
Figure 13 - Data Input and Output System
Two or three processor modules in a redundant arrangement are rated SIL 3,
however, a minimum of two processor modules in a redundant arrangement
are still required for architectures designed to meet SIL 2.
The T9401/2 digital input module (the same as the module for the SIL 2
controller) is rated SIL 3 as it stands. The only constraint is that the simplex
output stage will not drive an energize to action output for SIL 3 - this requires
a dual arrangement of output modules. This output configuration is applicable
for a de-energize to action output at SIL 3.
The second processor module supplies the increased fault tolerance and gives
the configuration its SIL 3 rating. If either processor module fails, the module
must be replaced in the MTTR.
This controller suits many applications needing a mixture of SIL 3 de-energize
to action and SIL 2 outputs which do not need the additional fault tolerance
offered by dual and triple modular redundant configurations. The possibilities
for expansion are the same as those for the SIL 2 controller.
To Next Page
Loading...
